Sorry, I should have been much more explicit with my assumptions.
1) Point-buy system from 3.X is in place and in use in 4E. Same start, same everything.
As you point out, there are 8s and 9s (and no stats below 8) present, which would indicate that point buy was used. I initially did this since I noted that the stat blocks were very close to what point-buy gives you (it's about the only way I use).
_If_ the pregens were randomly rolled--and I'd hate to see the thinking behind that move--then we have a rather large coincidence. If we get more character sheets and they all fall in the 28-29 mold, I'd say the coincidence stretches the boundaries of credulity.
While I'm pretty sure I could deliver a system that would start from zero, I'm not sure if that would be profitable since preliminary results (given above) seem to indicate that 3.X point buy was used to make these characters.
Edit: Half-elves may have a choice of stat. However, not knowing the bonuses that humans get, it's hard to say what might be hardwired. OTOH, 'hardiness of humans combined with the grace of elves' is the general consensus on the make-up of a half-elf, right? If so, then CON/CHA would work. If they got a choice, I would think it'd be between CHA and DEX, to signify the difference between Elf and Eladrin backgrounds.